1. Field of the Invention
The present invention relates to a vacuum switch and a vacuum switchgear, and more particularly relates to a vacuum switch and a vacuum switchgear that are suitable when the circumference of a vacuum chamber accommodating the switch unit is isolation-molded.
2. Description of Related Art
A vacuum switch is a switch that utilizing high-vacuum isolation performance; a compact, SF6 gasless switch can be achieved.
Some vacuum switches have isolation performance improved by not only vacuum insulation but also by the use of a double layered isolating structure in which the circumference of the switch chamber is covered with solid isolation resin.
When the circumference of the switch chamber of the vacuum switch is covered with solid isolation resin, however, an electric field is concentrated at the ends of an insulating cylinder constituting the switch chamber, causing dielectric breakdown to be likely to occur.
Accordingly, a vacuum switch in which the circumference of the switch chamber is covered with solid isolation resin and relief of electric field concentration at the ends of the insulating cylinder is considered is described in Patent Document 1.
Patent Document 1 discloses a vacuum switch in which electric field relieving shields, each of which is formed in a doughnut shape by connecting both ends of a spiral spring made of conductive metal or resin, are disposed at the ends of an insulating cylinder internally including a fixed electrode and a movable electrode to constitute a vacuum chamber and then these electric field relieving shields are covered by molding, so that electric field concentration at the ends of the isolating layer is relieved.    Patent Document 1: Japanese Patent Laid-open No. 2005-197061